1. Field of the Invention
The invention relates to novel fuel compositions and their use and more particularly concerns methods of improving the combustion of fuels such as ammonia, petroleum distillates, alcohols and amines by release of energy and hydrogen at the time of ignition.
2. Brief Description of the Prior Art
It is vital that new sources of high energy fuels be developed and that presently available substandard fuels be improved to raise their usefulness and efficiency. Prior hereto, it was appreciated that ammonia, petroleum distillates such as naphtha, benzene and the like, volatile alcohols and amines were fuels which upon combustion form combustion gases with considerably greater thermal energy than the initial combustion reactants. However, each of the above mentioned fuels has failed to achieve an important commercial position as an energy source. As fuels, ammonia, certain of the petroleum distillates, volatile alcohols and amines have shortcomings which can very generally be said to relate to an unsatisfactory combustion. The reasons for the unsatisfactory combustion are varied and individual to the particular fuel as will be described in greater detail hereinafter.
There is agreement among those who are knowledgeable in the field of energy fuels that hydrogen is the ideal fuel of the future, but that it will be decades before engineering has been developed to meet the practical requirements for utilization of hydrogen per se as a commercially significant fuel. The desirability of utilizing hydrogen as a fuel is based on three factors. First, hydrogen can be produced in abundance from abundant and inexpensive raw materials. Second, as a source of energy, hydrogen provides 61,000 BTU/pound upon combustion and third, the product of hydrogen combustion is water, which poses no pollution threat to the ecology.
To enhance the combustion of a number of conventional fuels and fuels of poor combustibility, it has been previously suggested to add gaseous hydrogen to the combustion mixture. The addition of hydrogen to combustion mixtures can provide additional thermal energy release, lower ignition temperatures, advance flame speeds, reduce the undesirable emissions of nitrogen oxides and carbon monoxide and generally effect a more efficient combustion. However, the previously proposed methods of adding hydrogen to combustion mixtures have consisted of adding gaseous hydrogen to the volatilized fuel at the time of ignition or just prior thereto; see for example U.S. Pat. No. Re. 28,547. The systems proposed heretofore for injecting gaseous hydrogen into a combustion mixture have been complex, costly and of questionable reliability. In general, the prior systems have required such things as a separate hydrogen injection system, including dual fuel supply lines; provision for generation and/or storage of hydrogen gas and new carburetion control systems and like complicated apparatus. As of this time, no commercial hydrogen gas utilizing system has been available because of the technical problems involved in meeting these requirements.
By the method of my invention, hydrogen is made available to the combustion mixture by dissolving a hydrogen carrier in the base fuel to obtain novel fuel compositions. The carrier releases hydrogen for combustion at the time of ignition and thus obviates the need for a separate hydrogen gas injection system, dual fuel supply system, special carburetion devices, fuel mixing controls and hydrogen gas releasing or generating and storage equipment. The fuel compositions of my invention are also advantageous in that the hydrogen carrier employed is a chemical compound which has chemically bound hydrogen. The release of hydrogen from the carrier occurs when the chemical bond is broken with a consequent release of energy. This energy release serves as an "energy kick" to assist ignition and boost combustion of the base fuel and the additive.
It was previously appreciated that ammonia in admixture with air forms an explosive fuel mixture which can operate internal combustion engines. However, ammonia has been considered inferior to hydrocarbons as a fuel because it has a relatively high ignition temperature in admixture with air, i.e.; on the order of about 780.degree. C. Furthermore, the explosive range of ammonia and air mixture is quite narrow, i.e.; within a range of about 16 to 25% by weight of anhydrous ammonia in admixture with air. This requires sensitive carburetors. Also the higher temperatures require different alloys and designs for the engine.
Illustrative of prior art attempts to obtain a satisfactory fuel composition based on ammonia in U.S. Pat. No. 2,559,605 which discloses the addition of an auxiliary gas to prime the explosion of a mixture of air and ammonia. Representative of the auxiliary gases disclosed are hydrocarbon gases, carbon monoxide, methanol vapors, methylether, ethylether, methylamine, ethylamine or a mixture of such gases. In U.S. Pat. No. 2,393,594 an attempt was made to upgrade ammonia as a fuel for use in internal combustion engines by dissolving ammonium nitrate (as an oxidizer) in liquid ammonia. The latter patent also discloses fuel mixtures of ammonia and low molecular weight alcohols with ammonium nitrate dissolved therein. Another approach is represented by U.S. Pat. No. 2,140,254 which discloses a device employing fuel mixtures for internal combustion engines comprising mixtures of ammonia with hydrogen gas and nitrogen gas. Other approaches to the use of ammonia as a fuel have included its admixture with hydrocarbon fuels for use in internal combustion engines (see for example U.S. Pat. Nos. 1,589,885; 1,671,158; and 3,150,645). Compositions of ammonia and at least 30% by weight of lithium borohydride are disclosed in U.S. Pat. No. 3,108,431 as rocket fuels, i.e.; fuels possessing hypergolicity.
Although it was previously known that certain borohydrides formed mono, di, tri and tetra-ammoniates (U.S. Pat. No. 3,108,431) and that certain boron compounds were advantageously used in admixture with liquid hydrocarbon fuels (see for example U.S. Pat. Nos. 3,738,819; 3,403,014; 3,215,740) it was not heretofore appreciated that minor proportions of these compounds could be employed to prime and enhance the combustion of ammonia-air mixtures.
In general, all of the prior art compositions and methods of employing ammonia as a fuel have not been entirely satisfactory for a number of reasons such as, for example, the difficulty in employing a relatively pure ammonia and obtaining the necessary high initial heat flash to bring about an auto-ignition. No commercial application ever resulted from such attempts.
The improvements of petroleum distillates such as gasoline as a fuel, by the addition of from 4 to 10% by weight of hydrogen gas to the vapors of gasoline has been suggested; see, for example, Chemical and Engineering News, Apr. 14, 1975, page 19. The benefits suggested include a reduction of nitrogen oxide emissions and carbon monoxide emissions due to the lower ignition temperatures associated with the mixtures. However, as discussed above, the difficulty of using hydrogen gas heretofore for its fuel potential, particularly as a motor fuel resides in the engineering problems of storing, transporting and adapting it to the automobile engine. These difficulties are overcome by the method of my invention. The addition of ammonia to improve hydrocarbon fuels is disclosed in U.S. Pat. Nos. 1,589,885 and 1,671,158.
Quaternary ammonium borohydrides are disclosed in U.S. Pat. No. 3,403,014 as useful when added to high volatility gasoline (Reid vapor pressure above 9) in proportions of from 0.001 to 0.1% by weight of the gasoline, as a cold weather anti-stalling additive.
Current interest in substitutes for petroleum based fuels has included the lower molecular weight, volatile alcohols such as methanol, ethanol and t-butanol which can be synthesized without resort to petroleum starting materials. Methanol has been thoroughly studied as a fuel (see for example Reed et al., Science 182, No. 4119, page 1299). The advantage of using methanol as a base fuel is related to its high octane rating, the lower combustion temperatures with consequent lower exhaust temperatures, lower emissions of nitrogen oxides and improved combustion of mixtures of gasoline with up to 15% by weight of methanol.
There are, however, disadvantages associated with the use of methanol, alone or in admixture with gasoline as a fuel. For example, methanol may require heating to volatilize. In addition, methanol has a low flame speed, corrodes engine parts (through aldehyde and acid formation) and lowers mileage per gallon (by a factor of 0.5) because of its lower energy value (in comparison to gasoline). By the method of my invention, methanol as a fuel may be upgraded in that combustion efficiency is improved, flame speed is increased, corrosion inhibited and the miles per gallon ratio improved.